Over the last several years it has become apparent that the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) is associated directly or indirectly with a number of physiological phenomena, including appetite, memory, thermoregulation, sleep, sexual behavior, anxiety, depression, blood pressure lowering and hallucinogenic behavior [Glennon, R. A., J. Med. Chem., 30, 1 (1987)].
It has been recognized that there are multiple types of 5HT receptors. These receptors have been classified as 5-HT.sub.1, 5-HT.sub.2, and 5-HT.sub.3 receptors with the former being further divided into at least the sub-classes 5-HT.sub.1A, 5-HT.sub.1B, 5-HT.sub.1c, and 5-HT.sub.1D. The binding affinity of a compound for one or more 5-HT receptors can provide a desirable physiological effect or minimize an undesirable effect. Therefore it is desirable to provide compounds which can bind to 5-HT receptors to act as serotonin agonists and antagonists.
Flaugh in U.S. Pat. No. 4,576,959 (issued 1986) and in European Patent Application 0153083 (published 1985) disclosed a family of 6-substituted-4-dialkylamino-l,3,4,5-tetrahydrobenz-[cd]indoles which are described as central serotonin agonists. Leander in U.S. Pat. No. 4,745,126 (1988) disclosed a method for treating anxiety in humans employing a 4-substituted-t,3,4,5-tetrahydrobenz[cd]indole-6-carboxamide derivative.
Pharmaceutical research has continued to focus on the provision of more active and safer agents for the regulation of the various serotonin functions. The present invention provides a series of new compounds having high potency as agonists for the regulation of serotonin functions.